For certain applications there is the necessity of providing a simple, inexpensive and reliable quick action shut off valve which interrupts and permanently closes a gas or liquid flow or a vacuum line.
Simple flow-actuated valves with valve members in the form of plates, balls or cones adapted to be closed by counter pressure, or by mechanical and/or electromagnetic forces, are known, for example, in German Pat. No. 2,638,879. These valves operate in such a way that they open when the fluid pressure increases above or falls below a certain value and then close again or vice versa.
There are furthermore applications, as for example, safety valves in the piping of toxic gases, in which the valve has to close when a defect occurs in order to prevent escape of the gas into the ambient atmosphere or, in another case, to prevent damage to vacuum apparatus by the ingress of air. In such cases, steps have to be taken to ensure that the defect does not entail undesired secondary effects.